The present invention relates to immunoassays for detection of phenylacetylglutamine (PAG) content in body fluids, and to novel antibodies and fluorescein conjugates useful in assays to detect PAG.
According to the 2 phenylethylamine (PEA) theory of affective behavior, an increase in the brain level of PEA may underline mania while a relative deficit may play a major role in certain forms of depression. Since phenylacetic acid (PAA) is formed metabolically by oxidative deamination of PEA, and PAA is excreted with urine almost entirely in its conjugated form as PAG, assays for monitoring PAG can be useful in diagnosing or monitoring mania or depression.
Techniques previously employed to determine PAG levels in blood or urine involve hydrolyzing PAG to PAA. The PAA is then quantified by fluorometric procedures (A. A. Boulton, Progr. Neurogenetics, 1:937 (1967) or gas chromatography; K. Blau, Clin. Chim. Acta, 27:5-18 (1970); H. Curtius et al., Clin. Chim. Acta, 27:277-285 (1972); Goodwin et al., Clin. Chim. Acta, 62:443 (1975); Davis et al., Journal of Chromatography, 222:161-169 (1981); Fellows et al., Biochemical Mass Spectrometry, Vol. 5, No. 8 (1978); Markin et al., Analytical Biochemistry, 99:283-287 (1979). Such tests are extremely time consuming. Typically, only several samples can be analyzed in a day. In addition, the equipment used in such analysis is expensive, often several hundred thousand dollars if gas chromatography and mass spectrometry are used.
As indicated above, applicants developed a new fluorescence polarization immunoassay test for PAG. Typically, for endogenous substances (PAG being an endogenous substance in the patient), the incubation times required for FPIAs for endogenous substances typically take a number of minutes. Thus, the total analysis time for a given sample can take anywhere from twenty to one hundred twenty minutes.